Used for the treatment of bone defects caused by injuries or diseases are the transplantation of an autogenous bone taken from a patient himself, the transplantation of a similar bone taken from another person, the implanting of an artificial bone made of a metal such as titanium or hydroxyapatite ceramics, etc. Hydroxyapatite ceramics can directly bond to bones because of bone conduction which is not owned by conventional metals, polymers and alumina ceramics. Therefore, they have been gradually finding applications as bone-repairing materials substituting for autogenous bones in wide regions such as oral surgery, neurological surgery, oto-rhino-laryngology, orthopedic surgery, etc. However, artificial bones of ceramics typified by hydroxyapatite are disadvantageously difficult to handle during operation because they are hard and brittle. To overcome this problem, a spongy, elastic apatite/collagen composite was developed. Although this material is easily handled, it cannot be used alone in a body portion subjected to stress because of low mechanical strength.
Resume of Lectures in 2008 Annual Meeting of The ceramic Society of Japan, page 324, lower column discloses a permeable, porous, cylindrical body, which is formed by rolling a wave-sheet-shaped hydroxyapatite/collagen nano-composite. This reference describes that this permeable, porous body has excellent tissue penetrability and bone conduction, because it has a hollow center portion similar to a relatively large medullary cavity, and penetrating pores formed on a peripheral surface to permit cells and tissues to enter. However, because this penetrable, porous body is formed by a wave-sheet-shaped composite and has a hollow portion similar to a relatively large medullary cavity, it has disadvantageously low strength despite excellent tissue penetrability and bone conduction.